A carbonaceous feedstock gasification system is a system which converts a carbonaceous feedstock into gas mainly containing CO, N2, or the like by gasifying agent containing oxygen or water vapor. In general, the carbonaceous feedstock gasification system is configured of a carbonaceous feedstock feeding system, a gasifier, and a char recovery system. The carbonaceous feedstock is fed to the gasifier by transport gas such as nitrogen, the gasifying agent (air, oxygen-enriched air, oxygen, water vapor, or like) is fed to the gasifier, the carbonaceous feedstock is combustion-gasified in the gasifier, and product gas (combustible gas) is generated. In addition, in the char recovery system, an unreacted portion (char) of a carbon-containing feedstock of the product gas is removed.
In the char recovery system in the above-described gasification system of the carbonaceous feedstock, the char contained in the product gas generated by the gasifier is removed using a plurality of stages of separation. In addition, the recovered char is returned to the gasifier by the char feeding unit. As the char feeding unit, a char feeding hopper is installed. When the recovered char is re-input to the gasifier, it is necessary to control an operation such that a recovery amount of the char and a feed amount of the char approximately balance with each other. Accordingly, it is important to correctly grasp the amount of retained char.
For example, PTL 1 discloses that a volume (level) inside a hopper is measured using a radiation source section and a γ-ray detector provided inside the casing tube.